If I hit a creature with an attack using a poison coated weapon (for example Purple Worm Poison) could I, rules as written, change the poison damage type to necrotic via the lvl 6 Undead Patron Warlock's feature Grave Touched? That reads:
[...] once during each of your turns, when you hit a creature with an attack and roll damage against the creature, you can replace the damage type with necrotic damage. While you are using your Form of Dread, you can roll one additional damage die when determining the necrotic damage the target takes.
There seem to be two conditions for the feature to be able to convert damage:
- The hit with an attack ("when you hit a creature with an attack")
- The roll of damage against the creature that was hit. ("and roll damage against the creature")
But it doesn't state, that the damage roll must be part of the attack that fulfilled condition 1. For comparison the lvl 3 Horizon Walker feature Planar Warrior reads:
The next time you hit that creature on this turn with a weapon attack, all damage dealt by the attack becomes force damage [...]
Here the damage to be converted explicitly must have been dealt by the attack.
Thus, if the damage roll in Grave Touched doesn't have to be dealt by the attack, could you choose which roll of damage you would convert as long as it happens in the same turn as the attack fulfilling condition 1. ? Or would it have to be the first instance of a damage roll after the hit? If so, could you use the blowgun and poison coated needles, since they don't involve a "roll" of damage but only a flat 1 point of piercing damage, making the applied poison damage the first instance of a damage roll after the hit?